Efficient injection of spin-polarized excitons and optical spin orientation of a single Mn2+ ion in a CdSe/ZnSe quantum dot

TL;DR

This paper demonstrates efficient injection of spin-polarized excitons into individual CdSe quantum dots and achieves optical spin orientation of a single Mn2+ ion within such a dot, advancing quantum spin control techniques.

Contribution

It introduces a method for efficient spin-polarized exciton injection and demonstrates optical spin orientation of a single Mn2+ ion in a quantum dot, revealing spin relaxation processes.

Findings

Spin-polarized excitons injected with ~40% polarization.

Spin relaxation occurs during exciton lifetime in quantum dots.

Optical spin orientation of a single Mn2+ ion achieved.

Abstract

Circularly polarized optical excitation is used to demonstrate the efficient injection of spin-polarized excitons to individual self-assembled CdSe quantum dots in ZnSe barrier. The exciton spin-transfer is studied by means of polarization-resolved single dot spectroscopy performed in magnetic field applied in Faraday configuration. Detailed analysis of the neutral exciton photoluminescence spectra reveals the presence of exciton spin relaxation during its lifetime in a quantum dot. This process is seen for both nonmagnetic dots and those containing single Mn$^{2+}$ ions. Taking this into account we determine the spin-polarization degree of excitons injected to a dot under circularly polarized below-the-barrier optical excitation at 488 nm. It is found to be close to 40% in the entire range of the applied magnetic field. Exploiting the established spin-conserving excitation channel we demonstrate the optical spin orientation of a single Mn$^{2+}$ ion embedded in a CdSe/ZnSe quantum dot.